Roofing and other weather exposed materials are exposed to the effects of sunlight and moisture resulting in physical and chemical changes, commonly called weathering. Initially, weathering results from the sun's ultraviolet rays which dull the color of the roof material, generally lightening the color of the roof. Gradually, the roof is colonized by microfungi which darkens the color of the roof material. As the roof continues to age, the surface and sharp edges of the roof are eroded by continued exposure to heat and cold and from abrasive particles carried by wind and rain. Roof material destroying organisms, such as moss, further degrade the roof's surface and edges. Loose debris from trees may begin to accumulate on the roof, particularly in recesses such as between shakes or tiles and in bends or corners of the roof. After each rain, these areas remain moist for a longer time than roof areas exposed to direct sunlight. Because of these moist conditions, moss growth is increased.
Moss damages the roofs in at least two ways. First, during a rain, the moss retards the shedding of water, which promotes leaks and roof rotting. Second, after the rain stops, the moss prevents the roof material from drying, which further encourages the growth of additional roof destroying organisms.
The most common currently used method for removing moss from roofs involves washing the roof under high pressure and then treating the roof with an oil-based sealer and/or U-V blocking agent such as zinc. During pressure washing, water is applied to the roof material at a pressure of approximately 2500 to 3500 pounds per-square-inch. Pressure washing removes most of the moss, but at the same time tears away the outer roof material. After pressure washing, the roof is thinner by as much as an eighth to a quarter of an inch. Thus, pressure washing removes years of useful life from the roof by literally removing the exposed outer surface of the roof material. Furthermore, after pressure washing, the former roof material must be cleaned out from gutters and off siding, windows, lawns, shrubs and sidewalks.
After pressure washing, oil-based sealing agents are applied to the roof material. It is believed that treatment with "replenishing oils" seals the roof against further weathering. However, the natural oil coating may actually provide an additional food source for moss. Furthermore, the petroleum-based oil products are likely to be oxidized (broken down) by sunlight, reducing the life of the oil, while increasing the flammability of the roof.
Another moss growth prevention method used after pressure washing involves metal based treatments. Typically, a zinc or other metal based solution is applied to the roof. However, these zinc and other metal based solutions are environmentally unsafe and often damage gutters, stain concrete, and poison the surrounding landscape.
The use of metals such as zinc and copper, to kill lichens, such as algae and fungi, on roofs is described in Little, U.S. Pat. No. 3,888,684. Specifically, Little describes granules coated with an inner and outer coating, each such coating containing algicidal compounds, such as zinc and copper ions. When exposed to moisture, the granules' inner and outer coatings leach the zinc and copper ions to produce a bimetallic effect to retard the growth of lichens, such as algae and fungi. The copper and zinc containing granules disclosed in Little have the disadvantage of being environmentally toxic. In addition, the granules themselves are easily washed off the roof by rain, thereby rendering the granules ineffective.
Lodge, U.S. Pat. No. 3,998,644, also describes a metal based roof coating for preventing algae growth. Specifically, Lodge describes an alkaline metal silicate with zinc hydroxychloride dispersed in a solution. The composition is applied to a roof, forming a hard coating on the roof. The zinc metal based treatment described in Lodge has the disadvantage of being environmentally toxic. An additional drawback is that the hard coating may break down during weathering, leaving portions of the roof unprotected.
No one has previously disclosed an environmentally compatible penetrant composition which is effective for preventing moss growth on roofs.
Therefore, objects of the present invention are to provide a stable, non-oil based, non-toxic, non-flammable composition which does not include toxic metals such as zinc or copper, which is cost effective to produce and apply, and effective for removing moss from numerous different porous weather exposed surfaces, particularly roofs, without pressure washing, without causing deterioration of gutters or downspouts, without harming plants or animals, resulting in a lengthening of the life of the weather exposed surface.